I was there <for> about one month.

[sunnyweather]

Hello,

A student of mine talked about her stay in London and she said:

'I was there about one month. I worked as an au-pair.'

I suppose she should have used 'for about one month.'

I was there for about one month.

Also, it seems to me that if we use 'for about one month' it is the same as 'for a month'.
In fact I even wondered if we can say 'for about one month' or 'for about a month'.

 

[JulianStuart]

The "for" is optional and with "about" the use of "a month" would be more common than "one month".